The present invention relates to a hinge mechanism for a vehicle seat assembly and in particular to a hinge mechanism including a leaf retaining spring for use with a seat assembly in which the seat back is rotatable to a forward dump position. The leaf spring is used to prevent rattling and vibration of the seat back during normal vehicle operation when the seat assembly is unoccupied.
Vehicle seat assemblies can be generally described as including a lower seat cushion and an upright seat back. Many seat assemblies, particularly those used in two-door motor vehicles, have a seat back that can be tilted forward from its normal upright position to a forward dump position to improve the access to the area behind the seat assembly. Such seat assemblies typically include an inertia locking mechanism to prevent forward rotation of the seat back when it is subjected to deceleration forces greater than a minimum value to prevent seat back rotation during a vehicle collision or during sudden stopping. Inertia latch mechanisms of this type typically allow the seat back to be rotated forward when not subject to deceleration forces by simply pushing the seat back forward.
A certain amount of free-play exists in these seat assemblies that allow the seat back to rotate forward slightly during deceleration particularly when the seat assembly is unoccupied. This slight forward rotation can cause a rattle that is annoying to the vehicle occupants. Various means have been developed to avoid such a rattle including the use of coil extension springs on the hinge mechanism to hold the seat back in its upright position. The spring is extendable to enable forward rotation of the seat back to the dumped position when sufficient force to overcome the spring is applied to the seat back. The spring is mounted to function as an over-center spring so that in the dumped position, the spring holds the seat back forward. The spring must then be overcome to return the seat back to its upright position. Such a spring mechanism requires mounting posts to be attached to both the seat back and the seat cushion which, along with the spring itself, adds to the cost and weight of the seat assembly.
Accordingly, it is an object of the present invention to provide an improved retention mechanism to hold the seat back in place to prevent rattling. It is a further object to provide a retention mechanism that does not also act to hold the seat back in the forward dump position as does an over-center coil spring.
It is a feature of the present invention to use a leaf spring retention mechanism that is configured to require no separate attachment to hardware.
It is an advantage of the present invention that once the seat back is initially rotated forward from the upright position that the leaf spring does not apply a force to hold the seat back in the dumped position.
In the preferred embodiment, the leaf spring is mounted at one end to the seat back arm of the hinge which supports the seat back. The seat back arm is pivotally attached to the seat bracket which is coupled to the lower seat cushion. The opposite end of the leaf spring is shaped to form a hook that is seated into a detent in the seat bracket or recliner plate if the seat assembly is equipped with a recliner.
To rotate the seat back forward, sufficient force must be applied to the seat back to unseat the spring hook end from the detent, permitting the seat back to rotate forward. As it rotates, the spring hook end slides across an arcuate edge surface of the seat bracket or recliner plate. Once the hook end is unseated from the detent, the spring no longer biases the seat back to any one position.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.